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Absorption spectrum in chlorophyll

  1. Feb 18, 2010 #1
    I have a question.

    We claim that the wavelength of a photon must exactly match the difference between the states of an atom or molecule. Then why are the peaks in the absorption spectrum of chlorophyll so broad? Shouldn’t they be very sharp?
  2. jcsd
  3. Feb 18, 2010 #2
    No, because it's a complex molecule, made of many tens of atoms:
  4. Feb 18, 2010 #3
    How come it takes so many photons to make a single sugar molecule via the C3 (Calvin) cycle photosynthesis? The heat of oxidation (to 6CO2 and 6H2O) of C6H12O6 is about 29 eV per molecule. Peaks in the absorption spectrum are less than ~2 eV per photon, so this implies over 15 photons per molecule. In fact studying the RuBisCO cycle implies ~4 photons per CH2O group, or ~24 photons per simple sugar molecule (monosaccharide). How many said photons have to hit the RuBisCO molecule in a millisecond to make the sugar molecule?

    Bob S
    Last edited: Feb 18, 2010
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